The invention relates to power transmission and, more particularly, to variable speed, V-belt power transmissions.
Variable speed, V-belt power transmissions are used quite extensively in all-terrain vehicles, golf carts, small trucks and snowmobiles. Such transmissions include a movable sheave member which is mounted on the driving portion of an input shaft for common rotary movement with the input shaft and for relative axial movement on the driving portion of the input shaft. This movement of the movable sheave member usually is accomplished by providing the driving portion of the input shaft with external splines and the movable sheave member with an internally splined portion or by providing the driving portion of the input shaft with a polygonal cross sectional shape, such as a square or hexagonal shape, and the movable sheave member with a driven portion having a corresponding shape. With either of these arrangements, manufacturing tolerances result in some circumferential play between the driven surfaces of the movable sheave member and the driving surfaces of the shaft driving portion causing a backlashing of the movable sheave member, i.e., oscillatory rotation of the movable sheave member relative to the input shaft, particularly when the input shaft is driven by a two- or four-cycle internal combustion engine which inherently imparts a cyclical torque on the input shaft. This backlashing is particularly prevalent when such engines are operating at idling speed or under low load conditions and, not only increases the rattling noise created by the movable sheave member, but also causes considerable wear of various components.